In practise such a solar power plant is known. FIG. 1 of this application shows in a schematic view such a conventional solar power plant. The shown configuration of the solar power plant is a practical accepted configuration which is build at a plurality of locations in the world. The solar power plant has a first and second circuit which are thermally coupled. The first circuit is a circuit for a solar heat transfer fluid, a solar HTF. The second circuit is a circuit for a mixture of water and steam.
The first circuit comprises a pump for circulating the HTF flow medium in the HTF circuit. Further, the first circuit comprises a solar field including at least one solar collector to transfer solar energy to the HTF flow medium. The HTF flow medium in the HTF circuit is heated by received solar energy. Normally, the first flow medium is an oil which is heated by the solar collector to a high temperature of at most 400° C. Care has to be taken to prevent the temperature of the flow medium to exceed above this maximum temperature of about 400° C. Above this temperature the oily HTF flow medium may rapidly deteriorate.
Heat energy of the HTF flow medium is transferred to the second flow medium by heat exchangers. The second circuit comprises a pump for circulating the second flow medium, a feed supply for supplying water, an economizer, an evaporator, a super heater, a re-heater and a steam turbine for generating electric energy out of steam. The steam turbine has nine sections, such that passing steam expands and cools down stepwise.
A drawback to the known solar power plant is the low availability. The availability of the solar power plant is dependent on many aspects. One major concern is that solar energy is only available during day time and influenced by weather conditions. No energy is generated during the night and less energy is generated during a cloudy day. Typically, the overall efficiency of the known solar power plant is about 35%.
EP 2.037.192 discloses a first steam circuit comprising a steam turbine and a gas turbine. Heat originating from the gas turbine is used in a waste heat recovery boiler to heat a water/steam mixture which circulates in the first steam circuit. A first steam supply piping is provided to supply steam from the waste heat recovery boiler to the steam turbine. A second steam supply piping is branched of the first steam supply piping to obtain a thermal coupling to transfer heat from a separately arranged second circuit to the first steam circuit.
The second circuit includes several heat collecting zones. The heat collecting zones are arranged in parallel and a heat transfer fluid is circulated by a pump. The second circuit comprises further a heat exchanging device to transfer heat from the second circuit to the water/steam mixture in the second steam supply piping of the first circuit.
A drawback of the disclosed configuration is that the efficiency of the total configuration is not satisfying.
DE 101 44841 discloses a steam circuit including a solar field. The steam circuit comprises a gas turbine. The gas turbine has a gas conduit to guide a flow of heating gas along several heat exchangers of the steam circuit. The gas conduit is subdivided into a first and second gas passageway. The flow of heating gas is distributed over the first and second gas passageway. The steam circuit has a water supply conduit which is branched to supply water through each gas passageway. The first and second gas passageways are each provided with respectively three heat exchangers which functions as an economiser, an evaporator and a superheater. The first gas passageway includes a solar field as an evaporator.
A first drawback of the disclosed steam circuit is that only one circuit including a water/steam mixture is provided. The water/steam mixture is supplied to the solar field which will result in a reduced efficiency. A further drawback to this known configuration is that the subdivided gas conduit provides constructional problems to build and operate the gas conduit. Further, the configuration includes double presented heat exchangers which increases costs to build the installation.
DE 196.51.645 discloses a configuration which presents a combination of a gas circuit and a steam circuit. The gas circuit includes a solar field to preheat supplied gas. The preheated gas is subsequently supplied to a gas turbine to generate electricity.
The steam circuit comprises a steam turbine. A steam flow is supplied to the steam turbine to generate electricity. The steam circuit is thermally coupled to the gas circuit by a heat exchanger to transfer waste heat originating from the gas turbine to the steam flow in the steam circuit.
A first drawback of the disclosed configuration is that the efficiency is not satisfying. A further drawback is that an operation of the gas turbine is always necessary to generate electricity. The solar field is arranged to preheat a gas flow, in which subsequently a fuel is mixed. It is not disclosed how to produce purely solar energy without the need of the fuel consuming gas turbine.
It is an object of the present invention to at least partially eliminate the above mentioned drawback and/or to provide a useable alternative. In particular, it is an object of the invention to provide measures which increase the availability of a solar power plant. More in particular, it is an object to provide at least one advantageous measure for the practical and accepted configuration of the solar power plant as shown in FIG. 1. In particular the invention aims to provide a solar power plant which is able to produce electricity from purely solar energy without CO2 emissions when sufficient solar energy is available during daylight.